Analysis of the impact of key strata failure on overlying strata and surface transport patterns

Abstract

After mining the coal seam under the slope terrain in the southwestern mining area, it is difficult to predict the damage characteristics of the overlying strata and the surface movement and deformation law. To solve this problem, this paper comprehensively analyses the key strata by applying the theory, similarity simulation and the GDEM simulation software, and explores the influence of the change of the key strata’s height and thickness on the damage characteristics of the overlying strata and the surface movement and deformation. By analysing the key strata in the “inclined step” structure, the minimum support force for the key strata not to slip is obtained, and the minimum support force required for the key strata at different levels is deduced. The results of similar tests and numerical simulation analyses show that the vertical displacement of the overburden and surface will be smaller as the key layer is further away from the coal seam. AT the same time, the damage to the overlying strata and the surface is smaller when the key strata fails, and the location of the first subsidence of the slope surface due to mining is usually located in the area close to the bottom of the slope. In the stable structure from the key strata to the ground surface, once the key strata is unstable and broken, the damage and vertical displacement of the ground surface will increase dramatically, thus causing a series of geological disasters such as ground subsidence. Therefore, before the key strata are broken, grouting reinforcement measures are carried out for the rock fissures below the key strata to enhance the tensile strength of the key strata, which can effectively reduce the surface subsidence and deformation.